Internet Engineering Task Force (IETF) S. Krishnan
Request for Comments: 6564 Ericsson
Updates: 2460 J. Woodyatt
Category: Standards Track Apple
ISSN: 2070-1721 E. Kline
Google
J. Hoagland
Symantec
M. Bhatia
Alcatel-Lucent
April 2012
A Uniform Format for IPv6 Extension Headers
Abstract
In IPv6, optional internet-layer information is encoded in separate
headers that may be placed between the IPv6 header and the transport-
layer header. There are a small number of such extension headers
currently defined. This document describes the issues that can arise
when defining new extension headers and discusses the alternate
extension mechanisms in IPv6. It also provides a common format for
defining any new IPv6 extension headers, if they are needed.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6564.
Krishnan, et al. Standards Track [Page 1]RFC 6564 Format for IPv6 Extension Headers April 2012Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................3
3. Applicability ...................................................3
4. Proposed IPv6 Extension Header Format ...........................4
5. Backward Compatibility ..........................................4
6. Future Work .....................................................5
7. Security Considerations .........................................5
8. Acknowledgements ................................................5
9. Normative References ............................................5
1. Introduction
The base IPv6 standard [RFC2460] defines extension headers as an
expansion mechanism to carry optional internet-layer information.
Extension headers, with the exception of the Hop-by-Hop Options
header, are not usually processed on intermediate nodes. However,
several existing deployed IPv6 routers and several existing deployed
IPv6 firewalls, in contradiction to [RFC2460], are capable of parsing
past or ignoring all currently defined IPv6 extension headers (e.g.,
to examine transport-layer header fields) at wire speed (e.g., by
using custom Application-specific Integrated Circuits (ASICs) for
packet processing). Hence, one must also consider that any new IPv6
extension header will break IPv6 deployments that use these existing
capabilities.
Any IPv6 header or option that has hop-by-hop behavior, and is
intended for general use in the public IPv6 Internet, could be
subverted to create an attack on IPv6 routers that process packets
containing such a header or option. Reports from the field indicate
that some IP routers deployed within the global Internet are
configured either to ignore the presence of headers with hop-by-hop
Krishnan, et al. Standards Track [Page 2]RFC 6564 Format for IPv6 Extension Headers April 2012